Identification of novel point mutations in the LBD of the RARα moiety of PML/RARα in RA-resistant APL.

(A) Schematic representation of PML/RARα, describing point mutations identified in ATRA-resistant APL cells from a patient in relapse and from a newly established cell line, NB4-MRA1, showing the approximate positions of 2 primers used in RT-PCR. (B) Summary of the LBD PML/RARα mutations identified in ATRA-resistant APL cell lines (numbers 1-6) and patients in relapse (numbers 7-17). Numbers 5 and 9 indicate the novel mutations in the LBD PML/RARα of ATRA-resistant APL cells identified and characterized in the current study and correspond to NB4-MRA1 and the patient, respectively. Numbers 1 to 17 in Figure 1B correspond to numbers 1 to 17 in Table 1. The lengths of the arrows reflect the frequency of each mutation. The position of the mutations is described with reference to normal amino acid sequence of RARα1.56 The alignment of the PML/RARα E-domain and TRβ ligand-binding domain by sequence homology indicates that the mutations in ATRA-resistant patients with APL and cell lines cluster in accordance with the regions in RTH syndrome denoted as I, II, and III. DBD indicates DNA-binding domain; LBD, ligand-binding domain; DD, dimerization domain; AF-2, ligand-dependent activation function.